Inner shell for a roof module in sandwich construction as well as method of producing same

ABSTRACT

An inner shell for a roof module in sandwich construction comprises an inner layer and a holding layer in which a reinforcement layer is embedded. The reinforcement layer is arranged within the holding layer at a side thereof which faces the inner layer. The holding layer is provided with pocket-like recesses on its side facing away from the inner layer which extend as far as to the reinforcement layer.

TECHNICAL FIELD

[0001] This invention relates to an inner shell for a roof module insandwich construction, comprising an inner layer and a holding layer inwhich a reinforcement layer is embedded, the reinforcement layer beingarranged within the holding layer at a side thereof which faces theinner layer.

BACKGROUND OF THE INVENTION

[0002] Such an inner shell is provided for being connected with an outershell in order to form a roof module in sandwich construction. In thisarrangement, the holding layer, with its side facing away from the innerlayer, is connected with the outer shell by means of gluing, clipping onor by other measures. As the reinforcement layer is arranged within theholding layer at the side thereof which faces the inner layer, therewill be a maximum distance between the neutral line, in case of bendingloads, of the roof module and the reinforcement layer; thus, thereinforcement layer offers the highest possible contribution to thestrength of the roof module.

[0003] Hitherto, a so-called spacer has been incorporated in the foam ofthe holding layer, which spacer has ensured that the reinforcement layeris located during foaming on the side of the holding layer facing theinner layer. A coarsely porous spacer mat could be used as spacer. Thespacer mat, however, is a costly component.

[0004] The object of the invention therefore consists in providing aninner shell of the type initially mentioned, which with small piece costcomprises a reinforcement mat that is precisely positioned in theholding layer. It is further the object of the invention to provide amethod of producing such inner shell.

BRIEF SUMMARY OF THE INVENTION

[0005] According to the invention, an inner shell for a roof module insandwich construction comprises an inner layer and a holding layer inwhich a reinforcement layer is embedded. The reinforcement layer isarranged within the holding layer at a side thereof which faces theinner layer. The holding layer is provided with pocket-like recesses onits side facing away from the inner layer which extend as far as to thereinforcement layer. The pocket-like recesses are the consequence of themethod employed for producing the inner shell. With this method, afoaming mold is made available which on one side is provided withnub-like projections. An inner layer is laid into the open foaming moldand a reinforcement layer is placed on the inner layer. An expandablematerial is then applied onto the reinforcement layer, such materialbeing capable of forming a holding layer in the cured state. Next, thefoaming mold is closed so that the projections rest at the reinforcementlayer and hold it against the inner layer, and the expandable materialis cured so that the reinforcement layer adjoining the inner layer isembedded into the holding layer during foaming. Positioning thereinforcement layer in the holding layer is thus not obtained any longerby a component which is embedded into each inner shell during foaming,but through the design of the foaming mold that is used for the foamingoperation. In adaptation to the respective demands, the size of therecesses produced in the holding layer and of the protrusions providedin the foaming mold, respectively, can be used as a trade-off betweennumerous parameters which are contrary in part. The lower limit for theportion of protrusions of the entire surface area is predefined by theflexibility of the reinforcement layer; i.e., the recesses have to bearranged so close to each other that the reinforcement layer can not goaway from the inner layer also in the intermediate regions where it isnot pressed—in the foaming mold—against the inner layer by theprotrusions. The upper limit for the portion of recesses of the entiresurface area is predefined by the required minimum strength of theholding layer as well as by the surface area, made available by it, forbeing glued together with the outer shell; the webs remaining betweenthe recesses must have specific minimum cross-sections and a specificminimum surface area. The size of the recesses has still furthereffects. The recesses form hollow chambers in the roof module which areof advantage in terms of acoustic properties. These effects can beoptimized by the design of the recesses. In addition, the volume of theholding layer is reduced due to these recesses, so that a smaller amountof expandable material has to be introduced during production. Costs arefurther reduced thereby. As long as the inner and outer shells are notglued together, the recesses in the holding layer also reduce thestrength of the inner shell, so that the latter can be folded moreeasily. Finally, the recesses reduce that surface area of the holdinglayer that is glued to the outer shell. Thereby, the separability ofinner and outer shells is facilitated during recycling. Size and numberof the recesses may differ from each other in distinct regions of theroof module, in order to make use of differing properties in theseregions.

[0006] Advantageous designs of the invention will be apparent from thesubclaims.

BRIEF DESCRIPTION 0F THE DRAWINGS

[0007]FIG. 1 schematically shows a roof including a roof moduleconfigured in sandwich construction;

[0008]FIG. 2 shows a section along plane II-II of FIG. 1;

[0009]FIG. 3 shows a detail of FIG. 2 on an enlarged scale; and

[0010]FIG. 4 shows in a schematic, perspective view a foaming moldincluding a holding layer and an inner layer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0011] In FIG. 1 there is shown schematically a vehicle with a vehicleroof 5 configured in sandwich construction. As can be seen in FIG. 2,the roof module consists of an outer shell 10 and an inner shell 12.

[0012] The outer shell essentially consists of an outer skin 14 whichmay be made of aluminum or plastics, and of a middle layer 16 made ofpolyurethane. The outer shell 10 is glued together with a longitudinalspar 20 of the vehicle body.

[0013] The inner shell 12 is formed essentially by an inner layer 22 anda holding layer 24 in which a reinforcement layer 26 is embedded. Theinner layer can be a mat of a pliant plastics which may be provided witha decorative coating. The inner layer may also be formed of a fabric ora knitting, which possibly is provided with a barrier layer of plastics.The barrier layer prevents that the material of the holding layerpenetrates the inner layer during foaming. The reinforcement layer 26may be a mat made of a glass fiber fabric.

[0014] For producing the inner shell 12, the inner layer 22 is laid intoa foaming mold. The foaming mold (in FIG. 4 schematically indicated byreference numeral 32) is provided with a plurality of (not shown)nub-like protrusions that have a rectangular basic shape here and tapertowards their free end. Taking the foamed product out of the foamingmold is facilitated thereby.

[0015] The reinforcement layer 26 is placed on the inner layer 22. Acurable, expandable material is applied onto the reinforcement layer 26.Then the foaming mold is closed, so that the protrusions of the foamingmold press the reinforcement layer 26 against the inner layer 22.Subsequently, the expandable material hardens to form the holding layer24 in which the reinforcement layer 26 is embedded. As a negative shapeof the nubs of the foaming mold 32, the holding layer 24 has a pluralityof pocket-like recesses 25. At the bottom of the protrusions and whenembedded in the holding layer 24, the reinforcement layer 26 ispartially exposed.

[0016] As can be seen from FIG. 2, the inner shell 12 and the outershell 10 are glued together in the middle of the roof module. As analternative, a textile adhesive connection (Velcro fastener) could beused. As the reinforcement layer 26 is located on the side of theholding layer 24 facing the inner layer 22, it simultaneously is locatedat a large distance from the neutral line of the sandwich roof module. Ahigh resistance to bending is ensured thereby. Towards the outer rim ofthe roof, the inner shell 12 is not glued to the outer shell 10, so thatit can be guided over the longitudinal spar of the vehicle as far as toa seal 34. The recesses 25 present in the holding layer facilitatebending the inner layer 12.

1. An inner shell for a roof module in sandwich construction, said inner shell comprising an inner layer and a holding layer in which a reinforcement layer is embedded, said reinforcement layer being arranged within said holding layer at a side thereof which faces said inner layer, said holding layer being provided with pocket-like recesses on its side facing away from said inner layer which extend as far as to said reinforcement layer.
 2. The inner shell according to claim 1, wherein said recesses have an essentially rectangular basic shape.
 3. The inner shell according to claim 1, wherein said recesses taper towards said reinforcement layer.
 4. The inner shell according to claim 1, wherein said recesses are arranged so as to lie uniformly side by side, a distance between neighboring recesses being smaller than a width of said recesses.
 5. The inner shell according to claim 1, wherein an outer shell is provided which is connected with said holding layer.
 6. The inner shell according to claim 5, wherein said holding layer and said outer shell are glued together.
 7. The inner shell according to claim 1, wherein said holding layer is connected with said outer shell by means of a Velcro fastener.
 8. A method of producing an inner shell for a roof module in sandwich construction, said inner shell comprising an inner layer and a holding layer in which a reinforcement layer is embedded, said reinforcement layer being arranged within said holding layer at a side thereof which faces said inner layer, said holding layer being provided with pocket-like recesses on its side facing away from said inner layer which extend as far as to said reinforcement layer, a foaming mold being made available which on one side is provided with nub-like projections, an inner layer being laid into said open foaming mold, a reinforcement layer being placed on said inner layer, an expandable material being applied onto said reinforcement layer and capable of forming a holding layer in a cured state, said foaming mold being closed so that said projections rest at said reinforcement layer and hold it against said inner layer, and said expandable material being cured so that said reinforcement layer adjoining said inner layer is embedded into said holding layer during foaming. 